<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>后盾人</title>
  </head>
  <body></body>
  <script>
    function hd() {
      let n = 1;
      return function sum() {
        console.log(++n);
      };
    }
    let a = hd();
    a();
    a();
  </script>
</html>
